Dear Elaine,
I too am a second wife and at the moment my stepsons are lovely but their mother is and has always been difficult, for them too at times and without a doubt when he dies there will be trouble although we have done our best to avoid it . The important thing to focus on is how much you loved Gary. I suspect for you , as for me with my husband, he was the love of your life, and how much of a hole in your life does someone like that leave? I know I would give every last penny to see my husband free of this terrible illness as would all the spouses who post here.
You were there for him and loved him when it mattered. Hold on to that.
With all good wishes Tre